JPH0192263A - Sealing medium for electronic part - Google Patents

Abstract

PURPOSE:To obtain a sealing medium for electronic parts, consisting of a wholly aromatic polyester of a specific structure and a specific granular inorganic material, having excellent moldability and heat resistance, especially solder resistance and useful as a sealing material for IC, transistors, etc. CONSTITUTION:A sealing medium obtained by blending (A) 100pts.wt. wholly aromatic polyester, consisting of (A) 30-80mol.% units expressed by formula I (4-oxybenzoyl), 10-35mol.% units expressed by formula II (terephthaloyl), 2.5-25mol.% units expressed by formula III (4,4'-dioxydiphenyl) and 5-30mol.% units expressed by formula IV (4,4'-dioxydiphenyl ether), having <=500P melt viscosity (at <=350 deg.C, 1,000/sec) and capable of preferably forming an optically anisotropic molten phase at <=350 deg.C with (B) 50-600pts.wt., preferably 100-400 pts.wt. granular inorganic material, preferably fused silica having 1-50mum average grain size and 2:1 average aspect ratio. The total amount of the units expressed by formulas III and IV is equimolar with that of the units expressed by formula II.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermoplastic encapsulant for electronic components, particularly a semiconductor encapsulant, and particularly relates to a thermoplastic encapsulant that has been proposed in the past. The present invention relates to a sealant characterized by having higher heat resistance than other sealants.

[Conventional technology]

1D child parts, especially semiconductor memory elements, should not be exposed to external moisture,
Inhibitors are used to protect against wood chips and the like. Currently used sealing methods include resin sealing and ceramic sealing, but recently resin sealing has been overwhelmingly popular. The reason why resin encapsulation is mainly used is that it is suitable for mass production and is therefore inexpensive.

Resin sealing is generally performed using a thermosetting resin material by a type of injection molding called transfer molding. As the thermosetting resin, novolak pregelatinized epoxy resin is generally used. The inhibitor is based on this epoxy main material, and contains a phenol novolak resin as a hardening agent, silica as a filler, and further flame retardants, coupling materials, and the like.

Such thermosetting resin encapsulation has the disadvantage that after molding, it is necessary to hold the mold at high temperature for a long time until the encapsulated resin is completely cured, and the molding cycle is long. Furthermore, since it is a thermosetting type, it is impossible to regenerate and reuse the Nuta Wrap that is inevitably generated during the process. For these reasons, complete automation of encapsulation molding for thermosetting resin encapsulation is impossible.

Furthermore, even when filled with inorganic compounds such as silica, the coefficient of linear expansion of epoxy thermosetting resin encapsulants does not decrease below a certain value, meeting future demands for lower stress in encapsulants. is not necessarily at a satisfactory level.

[Problem that the invention seeks to solve]

In recent years, sealing using a certain type of thermoplastic resin has been proposed to solve the drawbacks of the above-mentioned thermosetting resin sealing, particularly the process problems. For example, a method of sealing by injection molding using polyphenylene sulfide, polyether sulfide, polyimide, or thermotropic liquid crystal polymer has been proposed. Among them, thermotropic liquid crystal polymers are attracting attention as next-generation sealants because of their small coefficient of linear expansion and excellent heat resistance. For example, JP-A-60-40163 discloses an encapsulation molding method using a thermotropic liquid crystal polymer compound having a special terminal structure.

Thermotropic liquid crystal polymer, divided into thermotropic liquid crystal polyester or poly(ester-amide)
Under shearing, the melt viscosity is much lower due to molecular orientation, and even if filled with an inorganic material such as silica or alumina that reduces the coefficient of linear expansion of the molded product and increases thermal conductivity, the moldability remains low. It is attracting attention because of its excellent quality. However, when using a resin that can be molded at a temperature that can be easily carried out industrially, for example, within a temperature range of about 280 to 350°C, the heat resistance and wrinkle resistance of the resin are not necessarily guaranteed. This is not an industrially satisfactory level. In order to resin-seal electronic components using such a thermotropic liquid crystal polymer compound, it is desired to develop a material with a relatively low moldable temperature and excellent heat resistance.

[Means for solving problems]

In order to solve the above-mentioned problems, the inventors of the present invention have made extensive studies to find a material for encapsulating electronic components that has good moldability and excellent heat resistance, such as thermotropic liquid crystal polymers. The present inventors have discovered that a composition consisting of a wholly aromatic polyester with a specific structure and a specific particulate inorganic material meets the above objectives, and has completed the present invention.

According to the invention, the following repeating units 1, I
I, f [l and ■ (at least a part of the hydrogen atoms bonded to the ring may be substituted with a substituent)) such as 1, -0-C) -Co - 11, -oc (Fco - m, -o-c bread〇- ■, -o-o-o-o-o- 1 unit I is 30 to 80 mol, unit ■ is 10 to 35 mol, unit ■ is 2.5 to 25 Molch and unit ■ are 5 to 3
The total amount of the unit m and the unit (■) is present in the range of 0 mol.
50 at a temperature below ℃ and a shear rate of 1000 seconds.
There is provided an encapsulant for electronic components comprising about 50 to 600 parts by weight of a particulate inorganic material based on 100 parts by weight of a fully aromatic polyester having a melt viscosity of 0 voids or less.

The sealant of the present invention is characterized by good moldability and excellent heat resistance.

The repeating unit I in the fully aromatic polyester used in the present invention is a 4-oxybenzoyl moiety,
Derived from 4-hydroxybenzoic acid and their derivatives. In addition, in the unit (2), a 6-oxy-2-naphthoyl moiety can also be added within a range that does not impair the effects of the present invention. This may improve the moldability of the resulting sealant. The 6-oxy-2-naphthoyl moiety used is in an amount within the range of 10 mole or less in the wholly aromatic polyester, and the amount of the 4-oxy-naphthoyl moiety is within the range of 40 mole or less, usually 25 mole or less. It is also preferable in terms of the heat resistance of the resulting sealant.

Unit I is 30 to 80 mole in the wholly aromatic polyester;
Preferably it is present in an amount within the range of 40 to 75 mole.

The repeating unit (■) is a terephthaloyl moiety and is derived from terephthalic acid and its derivatives.

The unit (2) is present in the polyester in an amount ranging from 10 to 35 mole, preferably from 15 to 30 mole. In addition,
Other aromatic dicarboxy moieties, such as Lld, 4,4'-dicarboxydiphenyl, 2,6-dicarboxynaphthalene, or 1,3-dicarboxy, may be added to a part of the unit (2) within a range that does not impair the effects of the present invention. Dicarboxyphenyl and the like can also be added. In this case, the terephthaloyl moiety in the wholly aromatic dicarboxyl moiety is 50 mol or more, preferably,
It should be at least 75 moles.

The negative position ■ is the 4,4'-dioxydiphenyl moiety and L4
, 4'-dihydroxydiphenyl and its derivatives. The unit (2) is present in the polyester in an amount ranging from 2.5 to 25 mol, preferably from 3 to 20 mol.

Unit IV is a 4,4'-dioxydiphenyl ether moiety and can be derived from L4,4'-dihydroxydiphenyl ether and its derivatives.

The unit (2) is present in the polyester in an amount within the range of 5-30 mole, preferably 7-25 mole. When the unit (■) is present in an amount within the above range, the melting point of the resulting polymer is significantly lower than when the unit (■) is not present, and the flow properties are improved, resulting in significantly improved moldability. Despite this improvement, heat resistance is also high. Therefore, the flow characteristics of the sealant of the present invention are improved, and the heat resistance is maintained at a high level.

Incidentally, the total amount of the unit (■) and the unit (2) is substantially equal to the unit (■).

The wholly aromatic polyester used in the present invention is characterized by the use of 4,4-dioxydiphenyl ether, which is expressed in unitary units, and has good moldability and excellent heat resistance. , a wholly aromatic polyester with excellent solder resistance is obtained.

The fully aromatic polyester used in the present invention is 35
It is necessary to have a melt viscosity of 500 voids or less, preferably 100 voids or less under the conditions of a temperature of 0° C. or lower and a shear rate of 1000 seconds −1.

It is a polyester that forms a fusion. By forming an optically anisotropic melt phase, the melt viscosity is reduced under shear, making it easier to obtain a wholly aromatic polyester having a melt viscosity within the above range. Confirmation of the formation of an optically anisotropic molten phase can be carried out using a polarized light microscope equipped with a heating device, under direct Nicol light, as is well known to those skilled in the art. This can be done by observing a thin section under a constant heating rate and observing that light passes through at a certain temperature or higher. In this observation, the transmission of polarized light can be more reliably observed by applying slight pressure to the sample sandwiched between cover glasses at high temperatures, or by moving the cover glasses. In this observation, the temperature at which polarized light begins to pass through is the transition temperature to an optically anisotropic molten phase.

The wholly aromatic polyester used in the present invention has a concentration of 0.1 weight ft/volume in pentafluorophenol,
o,xdl/f or more, preferably 0.3 dt/f or more, more preferably 0.5 dl/g when measured at 60°C
or higher logarithmic viscosity. There is no critical upper limit for logarithmic viscosity, but it is usually 10 dt/f or less, preferably 7.5 dt.
/? Below, it is especially preferably 5a/2 or less. The maximum logarithmic viscosity can be determined from the melt viscosity and the mechanical properties of the resulting sealant.

Although the polyester of the present invention can be produced by various ester-forming reactions, it is usually produced by melt polymerization.

In the usual case, units (2), (2), and (2) are supplied in the form of a starting material compound having a hydroxyl group converted into a lower alkyl ester, and multipolymerization is carried out by the so-called acidolysis method. As the lower alkyl ester, acetic acid ester is most preferable.During polymerization, the presence of a catalyst is not necessarily required, but it is about 0.001 to 1% by weight, preferably about 0.005 to 0.5% by weight of the total leather weight. Use of known transesterification catalysts in amounts within the range of i% may also give favorable results in terms of polymerization rate. Specific examples of transesterification catalysts include alkali or alkaline earth metal salts of carboxylic acids, alkyl tin oxides, diaryl tin oxides, alkyl stannic acids, titanium dioxide, alkoxy titanium silicates, titanium alkoxides, Lewis acids, and hydrogen halides. can be mentioned.

The composition ratio of each folding unit in the polyester obtained by this method is substantially the same as the charged composition ratio of each raw material compound.

The encapsulant for electronic components of the present invention can be obtained by mixing and dispersing the above wholly aromatic polyester and particulate inorganic material. The amount of particulate inorganic material to be mixed is in the range of about 50 to 600 parts by weight, preferably 100 to 400 parts by weight of particulate inorganic material per 100 parts by weight of wholly aromatic polyester. Particulate inorganic materials include silica, talc, alumina, etc. Among them, silica, which is fused at high temperature and converted from crystalline to amorphous, has high purity and a linear expansion coefficient. Preferred because of its small size. The particulate inorganic material has an average particle size of about 1 to 50 μm, and an average aspect ratio of 2:1 or less so that anisotropy in the coefficient of linear expansion of the molding material does not occur due to the orientation of the inorganic material after molding. It is preferable. Fused silica that meets the above requirements has already been produced industrially and is already commonly used in epoxy resin sealants.

It is usually preferable that the surface of the particulate inorganic material be subjected to a suitable surface treatment in order to increase its affinity with the wholly aromatic polyester. Suitable surface treatment agents of the present invention include, for example, γ-glycidoxyprobyltrimethoxysilane, β
- Epoxy silane coupling agents such as (3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltribenoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)3 Examples include amine-based silane coupling agents such as -aminopropylmethyljethoxysilane.

The mixture of wholly aromatic polyester and particulate inorganic material is mixed with a crosstalker within the temperature range in which the wholly aromatic polyester is melted.
- Performed by known melt mixing techniques using a axial extruder or a twin-screw extruder. The mixing operation is carried out for about 1 minute to 30 minutes at a temperature higher than the melting point or crystal-to-liquid crystal transition temperature of the wholly aromatic polyester used, preferably 50° C. higher than said temperature. The particulate inorganic material is substantially uniformly dispersed within the wholly aromatic polyester. The resulting mixture of wholly aromatic polyester and particulate inorganic material is pelletized and used as a sealant for electronic components. The encapsulant of the present invention has excellent heat resistance and is therefore particularly suitable as an encapsulant for semiconductor integrated circuits. Encapsulation molding using the encapsulant of the present invention produces approximately 270 to 39
It is carried out by conventional injection molding at barrel temperatures in the range of 0°C. Mold temperature is 50-150
The temperature is preferably selected from within the range of 70 to 130°C. Encapsulation molding using the sealant of the present invention takes a shorter time, e.g.
Another feature of the present invention is that the molding cycle is performed within minutes. Furthermore, the encapsulant of the present invention has significantly higher heat resistance, for example, solder resistance, than conventionally proposed encapsulants made of thermoplastic resin, so it can withstand high-temperature soldering such as infrared 70-soldering. It's watery. Also,
The sealant of the present invention also has a low coefficient of linear expansion, which is a characteristic of sealants made of thermotropic liquid crystal polymers, and also has extremely low levels of water-extractable alkali metals and halogens.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 In a stainless steel reactor of content 201, equipped with a stirring device, gas inlet, distillation head and condenser, 2268 f (12,6 mol) of 4-acetoxybenzoic acid, 69 mol of terephthalic acid were added.
7.2f (4,2 mol), 4,4-diacetoxydiphenyl 567M (2,1 mol), and r) 4.4'
-diacetoxydiphenyl ether 600.6F (2,
1 mol) was added. The reactor is then evacuated to vacuum,
After purging with nitrogen three times, it was immersed in a bath maintained at 250° C. while flowing dry nitrogen at a rate of about 10 1/hour. After the contents of the flask began to melt and became a slurry, stirring was started and the temperature was maintained for 25 minutes. Then about 10
The pass salt was raised to 280°C over several minutes, held at the same temperature for 25 minutes, and then the pass salt was further raised to 320°C.
By this time, approximately 1.1j of acetic acid had been distilled out. Next, the pressure inside the system was gradually reduced to 20°C mHf in 10 minutes. Thereafter, the temperature of the pass salt was raised to 340°C, and the degree of vacuum was maintained at 0.4 vmHf to continue polymerization. After 10 minutes, the stirring was stopped, nitrogen was introduced, the pressure in the system was brought to normal pressure, and the pressure was further increased to 4 kg/d.
It was dried for 10 hours at 9°C. The resulting polymer was dissolved in pentafluorophenol at a concentration of 0.1 wt/vol.
It exhibited a logarithmic viscosity of 1.70 dllt when measured at °C.

Note that the logarithmic viscosity of 71 nh is calculated by the following formula.

tO: Falling time of pentafluorophenol, a solvent, when measured at 60°C using an Ubbelohde viscometer.

t: Falling time of the solution dissolving the sample OC: Concentration of the sample C9/di'') Microscopic pieces of this polymer were heated in a nitrogen atmosphere in a microscope heating device TH-600 manufactured by Linkam Co., Ltd. for 1 hour.
When the temperature was raised at a rate of 0°C/min and observed under a polarizing microscope with crossed Nicols, light began to pass through at 290°C and reached 300°C.
It was confirmed that the present polymer, which transmits a larger amount of light in the vicinity, forms an optically anisotropic molten phase at this temperature. Furthermore, when measured using DSC (Mettler TH3000) at a temperature increase rate of 20°C/min, an endothermic peak was observed at 296°C.

This polymer was subjected to 500 MHz 1H-NMR (J
When measured using EOL GX-500), it was confirmed that the polyesters had the same composition within the molar ratio of the charged raw materials and the analysis accuracy.

This polymer was produced using a cavilograph (Toyo Seiki Hs583).
The melt viscosity was measured using a nozzle with a diameter of 1 m and a hole length of 10 m at 320°C and a shear rate of 1000 sec-1.
It was 30 poise.

This polymer was heated at a cylinder temperature of 320°C and a mold temperature of 10°C.
When the solder resistance of the test piece (thickness 3 m) obtained by injection molding was evaluated at 0°C, it was found that the solder resistance at 300°C
The appearance did not change at all even after being immersed in the solder bath for 20 seconds. Further, the heat distortion temperature of this test piece was measured under a load of 18.5 kgf/- according to JIS K-7203, and was found to be 243°C.

Next, using a twin-screw extruder TEX-30 manufactured by Japan Steel Works, 100 parts by weight of the above fully aromatic polyester was mixed with fused silica (GR-80 manufactured by Toshiba Ceramic, average particle size 20 μm).
) were melt-mixed at a ratio of 250 parts by weight. The surface of this fused silica was subjected to surface treatment using a coating material of 1% by weight of γ-glycidoxybrobyltrimethoxysilane (5H-6040 manufactured by Toshi Silicone Co., Ltd.) in a conventional manner. The barrel temperature of the extruder is 300℃, and the screw rotation speed is 30.
At 0 rpm, the rotation direction was in the opposite direction and the average residence time was 8 minutes.

The thus obtained mixture of wholly aromatic polyester and fused silica was press-molded into a thin film and observed under a microscope, and the silica was found to be substantially uniformly dispersed. Further, the mixture of this wholly aromatic polyester and fused silica has a shear rate of 1000 seconds and a melt viscosity of 60 at 330°C.
0 voids were obtained. Using the thus obtained mixture of wholly aromatic polyester and fused silica, a test semiconductor device was injection molded. A good element was produced under the conditions that the barrel temperature was 330°C, the mold temperature was 150°C, and the molding cycle was 10 seconds. No displacement or damage to the lead wires of the injection molded product was observed.

In addition, when we evaluated the solder resistance of test pieces of encapsulated molded products obtained by injection molding using the same method as fully aromatic polyester polymers, we found that the appearance remained unchanged even after being immersed in a 300°C solder bath for 60 seconds. There was no change at all.

The volume resistivity of this sealed molded product is 1.7 x 1016
It was Ω・Vice.

Example 2 A wholly aromatic polyester represented by the following compositional formula was synthesized according to the method of Example 1.

To +0C-O-O+o6o+0C-Q-CO. ÷o (
×Suo frog.

÷o-o-o-c door, 15 The logarithmic viscosity of the obtained polymer was measured in the same manner as in Example 1, and it was found to be 1.41 dl/P. An anisotropic melt phase was formed.

Melt viscosity was measured in the same manner as in Example 1 and found to be 300.
℃, shear continuous [approximately 20 voids at 1000 sec-1.

This polymer was heated at a cylinder temperature of 310°C and a mold temperature of 10°C.
Injection molding was carried out in the same manner as in Example 1 under conditions of 0°C, and the solder resistance of the obtained test piece was evaluated.
The appearance did not change at all even after being immersed in a 0°C solder bath for 20 seconds. Further, the heat distortion temperature of this test piece was 238°C.

Next, a homogeneous mixture of wholly aromatic polyester and fused silica was obtained in the same manner as in Example 1 except that 200 parts by weight of fused silica was added to 100 parts by weight of the above wholly aromatic polyester, and then Example 1 When the solder resistance of the test piece obtained by injection molding was evaluated in the same manner as above, it was found to be 30
There was no change in appearance even after immersion in a 0°C solder bath for 60 seconds.

Example 3 Based on the method of Example 1, a wholly aromatic polyester represented by the following compositional formula was synthesized.

(-QC-o-cO%, -fOC[nCO-%2□5+
O%0-)Th, 1□.

Published by -o-o-o-o, 10 The logarithmic viscosity of the polymer obtained in the same manner as in Example 1 was 1.73 dt/l. An anisotropic melt phase was formed. Melt viscosity was measured in the same manner as in Example 1 and found to be 320°C.
, about 20 voids at a shear rate of 1000 s-1.

This polymer was heated at a cylinder temperature of 320°C and a mold temperature of 10°C.
The solder resistance of the obtained test piece was evaluated by injection molding in the same manner as in Example 1 under the condition of 300°C.
Even after being immersed in a solder bath for 20 seconds, the appearance did not change at all. Further, the heat distortion temperature of this test piece was 247°C.

Next, a homogeneous mixture of wholly aromatic polyester and fused silica was obtained in the same manner as in Example 1 except that 200 parts by weight of fused silica was added to 100 parts by weight of the above wholly aromatic polyester. In the same manner, the test pieces obtained by injection molding were evaluated for their anti-scratch properties, and were found to be 30.
There was no change in appearance even after 60 seconds of immersion in a 0°C non-dia bath.0 Comparative Example 1 According to the method of Example 1, 4-acetoxybenzoic acid, terephthalic acid, 4.4'- diacetoxyphenyl and 4
, 4-diacetoxydiphene; molar ratio of ether is 6
Each compound was charged and polymerized so that the ratio was 0/20/17.5/2.5. In the late stage of the reaction, the viscosity within the system increases significantly, and especially when the pressure inside the system is reduced, a portion of the system solidifies.
It became impossible to stir uniformly. Although the bath salt was further raised and maintained at 400°C, it did not melt and it was impossible to stir it uniformly.

Comparative Example 2 In Example 1, 4-acetoxybenzoic acid, terephthalic acid, 4.4'-diacetoxydiphenyl and 4.4
The molar ratio of '-diacetoxydiphenyl ether is 20/
Each compound was charged in a ratio of 40/30/10. Polymerization was carried out at this composition ratio in the same manner as in Example 1, but
When the bath salt was raised to 320°C and some time passed, the viscosity in the system increased significantly. When the temperature was raised to 340°C and pressure reduction was started, the inside of the system solidified and became impossible to stir.
Furthermore, the temperature of the bath salt was raised to 400°C, but it did not melt in the system.

Comparative Example 3 According to the method of Example 1, 4-7cetoxybenzoic acid, terephthalic acid, 4,4-diacetoxydiphenyl and 4
．． The molar ratio of 4-diacetoxydiphenyl ether is 2
Each compound was charged so that the ratio was 0/4015/35.

Polymerization was carried out in the same manner as in Example 1, except that the bath salt was
After raising the bath salt to 0℃ and some time elapsed, the viscosity in the system increased significantly, and even when the bath salt was raised from 340℃ to 380℃, the system did not melt at all and remained powdery, resulting in further polymerization. It was impossible to continue.

〔Effect of the invention〕

According to the present invention, there are provided various inhibitors for electronic components made of a wholly aromatic polyester and a particulate inorganic material, which have excellent moldability, excellent heat resistance, and especially excellent solder resistance.

This sealant is useful as a sealing material for ICs, transistors, capacitors, diodes, and the like.

Patent applicant: RiRashi Co., Ltd.

Claims (6)

[Claims] (1) Essentially the following repeating units I, II, III and
IV (at least some of the hydrogen atoms bonded to the ring may be substituted with a substituent) I, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ II, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ III, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ IV, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Unit I is 30 to 80 mol%, Unit II is 10 to 35 mol%, Unit III is 2.5 to 25 Mol% and unit IV are from 5 to
present in the range of 30 mol %, and the total amount of unit III and unit IV is present in substantially equal number of moles as unit II;
About 50 to 600 parts by weight of electrons made of particulate inorganic material per 100 parts by weight of fully aromatic polyester having a melt viscosity of 500 voids or less under the conditions of a temperature of 50°C or less and a shear rate of 1000 seconds^-^1 Sealant for parts. (2) The encapsulant for electronic components according to claim 1, wherein the wholly aromatic polyester is a polyester that forms an optically anisotropic melt phase at a temperature of 350° C. or lower. (3) The wholly aromatic polyester has a logarithmic viscosity of 0.1 dl/g or more when measured at 60° C. at a concentration of 0.1% by weight/volume in pentafluorophenol. The encapsulant for electronic components according to item 1. (4) The encapsulant for electronic components according to claim 1, wherein the particulate inorganic material has an average particle size of about 1 to 50 μm and an average aspect ratio of 2:1 or less. (5) The encapsulant for electronic components according to claim 1 or 4, wherein the particulate inorganic material is fused silica. (6) The electronic component according to any one of claims 1 to 5, comprising about 100 to 400 parts by weight of particulate inorganic material based on 100 parts by weight of wholly aromatic polyester. Sealant.